Switch to Xenial: salt-formula-jobs
Switch to Xenial: salt-formula-jobs

salt repos only have master branch, switch the single job directly to
xenial.

Change-Id: I760fc60179eb8b582c356295a66cc35501d5d9c3

Tesora/tesora-project-config,openstack-infra/project-config,openstack-infra/project-config,Tesora/tesora-project-config